can i get UNIX kernel and compile it like Linux ?

http://www.unix.com –
I am not a newbie to Linux, i have been using Linux as my desktop for 4 years, but i am just an end user to Linux, no advanced knowledge to it.
I knew that, i can download generic linux kernel and compile it by myself, but how about Unix? how can i get an Unix kernel and compile it ? or no this thing?
(HowTos)

Stories similar to can i get UNIX kernel and compile it like Linux ?

I am looking for some tutorials where I can learn to compile Linux kernel and create my own Linux distro. I don't want to create a copy of Ubuntu or I don't want to install my compiled codes in Ubuntu. I want to create new linus OS which I can share with my friends. I want to know that how can I create desktop graphics in my custom OS and other features like Ubuntu.

Unix like kernels were in picture from a long time. But due to its limitations it is not as successful as linux kernel. What are those limitations.
Basically I want to understand the fundamental/advanced points which describes the differences between Linux kernel and Unix like kernels? Please be specific to Linux and Unix internals only.